Wind Power Part 4: Components and Maintenance Small Wind San Jose State University FX Rongère March 2008

Inside a Wind turbine GE Wind 1.5 MW

Inside a Wind turbine

Generator Tri-phase Synchronous Generator The central magnet rotates with the rotor shaft of the turbine A variable Magnetic Field is inducted in the stator generating an Alternative Current When connected to the grid the generator is forced to rotate at constant speed To gain flexibility, the connection to the grid will be indirect with a double conversion AC-DC, DC-AC

Generator Tri-phase synchronous Generator Central magnet may be electromagnets fed by the grid Central magnet may be permanent using Rare Earth Metals* Increasing the number of poles one can reduce the rotation speed of the generator * In fact, the rare earth metals are not rare and new technologies are based on permanent magnets

Generator Tri-phase Asynchronous Generator The magnet of the rotor is replaced by a squirrel cage When the cage turns faster than the magnetic field in the stator it generates a high current in it and then a magnetic field which will play the same role as the magnet The current generated will depend of the difference of rotation between the rotor and the magnetic field in the stator: it is called the slip (typically 1%) To gain flexibility on the rotation speed of the shaft the slip will be varied using a variation of its electrical resistance Rotor of an asynchronous generator

Gear Box Tip speed ratio issue for large turbines Tip speed ratio ( λ ) is limited Typically, for a 3 blade turbine is: 3< λ <5

Gearbox Rotation speed decrease with the size of the turbine 100 kW 1,000 kW 2,500 kW 5,000 kW 500 kW

Gearbox Torque increases a lot with power

Gearbox Converts few rotation/mn in 1,500/mn The gear ratio may be 50, 100 or more Causes of wind turbine failures Source: Condition Monitoring of Wind Turbines, David Infield 1.5 MW gearbox and drive train

Gearbox Cost of repairs

Gearbox Multi-stage gearbox Planetary gearbox Low speed mainshaft Intermediate speed stage High speed stage Generator

Gearbox Multi-drive train Multi-drive train developed by Clipper Windpower in with eight generators around the main shaft. The Liberty turbine currently commercialized has four generators

Yaw Drive and Pitch Drive The yaw drive maintains the wind turbine facing into the wind It is similar to a tracker for a solar panel The pitch is the angle of attack of the blades in the wind flow Optimizing the pitch allows to improve efficiency for different wind speeds

NREl wind lab: NWTC Located in Denver (Co) 2.5 MW Dynamo-meter Structural blade testing Environment chamber at -60 o F Field testing

Offshore Wind Technology for the Offshore oil industry

Wind resource in California Solano 415 MW Altamont Pass 586 MW

Wind resource in California San Gorgonio 619 MW Tehachapi 665 MW Pacheco 16 MW

Offshore Wind Offshore projects up to 2004 About 460 MW Source: Offshore Wind Experiences - IEA

Offshore Wind Projects in the USA (2007) Cape Wind (Cape Cod / Nantucket Sound) Bluewater Wind (Long Island) Nai Kun (Hecate Strait) Galveston Offshore Wind (Texas)

Cost of a wind turbine Project cost including connection Turbine cost

Component costs Cost of the components of a wind turbine Ref: M. Gower Mat UK Energy Materials Review Material R&D Priorities for Wind Power Generation June 15, 2007 REpower MM99 wind turbine

O&M costs O&M costs represent 10% to 12% of the cost per kWh

Price /kWh The prices in the LB database reflect the price of electricity as sold by the project owner reduced by the receipt of any available state and federal incentives (e.g., the PTC Power Tax Credit), and by the value that might be received through the separate sale of renewable energy certificates (RECs)

Environmental Issues Noise Visual impact Construction impact Avian impact Source: m 250 m

Avian Impact Source: National Wind Coordination Committee, Fact sheet Nov. 2004

Avian Impact Source: National Wind Coordination Committee, Fact sheet Nov. 2004

Avian Impact Source: National Wind Coordination Committee, Fact sheet Nov. 2004

Avian Impact Main accidental death causes for birds Source: Mick Sagrillo PUTTING WIND POWER'S EFFECT ON BIRDS IN PERSPECTIVE 2003 * Number estimated using the ratio per MW provided by the NWCC multiplied by the installed wind power in the USA in 2006 (15,575 MW)

Wind Turbine (400 W-100 kW) Guyed or Tilt-Up Tower ( ft) Safety Switc h Power Processing Unit (Inverter) Cumulative Production Meter AC Load Center Small Wind

Factors to consider Good wind resource: Class 2 or better Home or business located on 1 acre or more of land Average monthly electricity bills >$100 for 10 kW system, >$50 for 5 kW system Zoning restrictions, economic incentives

Modern Small Wind Turbines Small turbines range from 20 W to 100 kW Only 3-4 moving parts means very low maintenance 20- to 40-year design life Proven technology – 150,000 installed; over a billion operational hours 1.8 kW

Installation Cost Estimate $2-4/installed watt for typical system Smaller systems require smaller initial outlay, but cost more per watt Taller towers cost more, but usually reduce the payback period A 4-10 kW system can meet the needs of a typical home Customers paying 12 cents/kWh or more for electricity with average wind speeds of 10 mph or more can expect a payback period of 8-16 years

Example

Building integration Examples of projects integrating wind power in buildings

Companies to follow (Southwest Wind)

Wind development worldwide Major Wind Development countries